The present invention relates to an electric machine,                wherein the electric machine has a housing in which a stator is disposed and in which a rotor is rotatably mounted about an axis of rotation,        wherein the housing extends from a front end to a rear end, viewed in the direction of the axis of rotation,        wherein the housing either has an air inlet opening near the front end and an air outlet opening near the rear end, or has an air inlet opening near the front end and rear end and, therebetween, an air outlet opening on a side parallel to the axis of rotation,        wherein during operation the electric machine aspirates air at the air inlet openings and expels the aspirated air at the air outlet opening,        wherein an attachment is mounted on the side of the housing parallel to the axis of rotation, said attachment covering the air inlet openings and the air outlet opening in the manner of a hood so that the air expelled from the housing at the air outlet opening is returned to the air inlet openings.        
Electric machines of this kind are well known. Reference is made to DE 37 24 186 A1 purely by way of example.
In the case of electric machines of the type mentioned in the introduction, pipes for a gaseous or liquid cooling medium—generally air or water—are usually disposed in the attachment and extract heat from the air cooling the electric machine. Because of the installation space required for the pipes, the attachment generally has to have a considerable overall height. Moreover, although the cooling of the electric machine is efficient, it is not optimum.